Observations on the microvascular repair process after confluent argon laser photocoagulation.

We observed the repair process of the choriocapillaris after confluent argon laser retinal photocoagulation in the domestic cat with a plastic injection-corrosion technique coupled with scanning electron microscopy and transmission electron microscopy. Confluent photocoagulation was applied to the area of the retinal tapetum, creating two kinds of lesions: one consisted of five confluent burns and the other of 20 confluent burns. Specimens were prepared at 1, 30, and 60 days. Occlusion of the choriocapillaris was noted regardless of the length of time after photocoagulation. The only sign of repair was noted at 60 days when the choriocapillaris located at the edge of the lesion showed a uniform rearrangement. Transmission electron microscopy revealed severe damage to the endothelial cells, with lack of cell activation and permanent capillary closure in the vessels of the lesion proper.

Choroidal microvascular repair after argon laser photocoagulation. Ultrastructural observations.

Acute laser injury to the tapetum of the feline retina produces thrombosis of the choriocapillaris. Early changes are characterized by the appearance of platelet-fibrin thrombi within capillary loops and disruption of endothelial integrity. By 4 days, thrombi have disappeared, and the endothelium shows regenerative changes. No endothelial cell mitotic activity is seen. The endothelial cytoplasm becomes plump, and there is a loss of the fenestrations adjacent to Bruch's membrane. By 10-20 days, the capillary structure shows gradual restoration. At 30 days, endothelial cell fenestrae are clearly evident adjacent to Bruch's membrane. The reparative process in this model appears to evolve as a result of thrombolysis and endothelial cell activation.

Enlargement of the optic disk in childhood optic nerve tumors.

Two children, a 9-year-old girl and an 8-month-old girl, were first examined because of unilateral proptosis. Both children were found to have unilateral optic nerve glioma, accompanied in the second case by neurofibromatosis. Two years after Patient 1 was first examined, the initial findings of thin vertical retinal striae and a gray opacification of the peripapillary retina had resolved. The enlarged left optic disk had an average diameter of 2 mm while that of the normal right optic disk was 1.6 mm. The disk-arteriolar ratio was R.E.:16:1 and L.E.: 20:1. Four years later, the patient's visual acuity was still 20/20 in both eyes and the only visual field abnormality was an enlarged blind spot corresponding to the enlarged left optic nerve head. Fundus photographs, orbital echography, and computed tomography showed no change in the size or location of the optic nerve glioma during the six-year follow-up period. In Case 2, the initial intraocular pressure was higher in the proptotic right eye than in the left eye (25 vs 19 mm Hg), but subsequent intraocular pressures were within normal limits and approximately equal in the two eyes. The disk-arteriolar ratio was R.E.:21:1 and L.E.: 18:1 and the cup-disk ratio was R.E.: 0.7 and L.E.: 0.3. Computed tomography disclosed an enlarged right retrobulbar optic nerve, a superior orbital fissure that was much larger on the right than on the left, and a larger cavernous sinus on the right. The right sphenoid bone was partially absent. Despite mild developmental delay, the patient's visual acuity apparently remained normal and the ophthalmologic findings did not change significantly during the 18-month follow-up period.

Congenital ocular toxoplasmosis.

Congenital ocular toxoplasmosis is a significant cause of blindness. Retinochoroiditis is the most common finding, but other ocular manifestations include microphthalmus, nystagmus, strabismus, and ptosis. The serologic tests and lymphocyte stimulation test are the most useful aids in making the diagnosis. Pyrimethamine, sulfonamides, and corticosteroids are useful to treat active lesions. Primary care physicians, obstetricians, and ophthalmologists may help to prevent transmission of the disease and its serious ocular sequelae.

Congenital toxoplasmosis associated with acquired oculomotor nerve (CN III) palsy.

A nine-week-old Caucasian male presented with right ptosis and right exotropia due to a third cranial nerve palsy. Symmetrical macular lesions and a paramacular hyperpigmented lesion with overlying vitreous cells in the left eye were compatible with congenital toxoplasmosis. Computer tomography demonstrated calcifications in the periventricular and midbrain regions where the oculomotor nerve exits the brainstem. The diagnosis was confirmed by the toxoplasma indirect fluorescent antibody titer greater than 1:2048 for the infant and greater than 1:512 for the mother. Treatment was instituted with pyrimethamine, sulfadiazine and folinic acid. Neurologic sequelae included a right hemiparesis, infantile seizures, and generalized developmental delay. A Mueller's muscle resection (RUL) combined with 9-mm recession of the right lateral rectus and 7-mm resection of the right medial rectus muscles produced minimal ptosis and right exotropia one year later. the child now prefers to fix with the right eye and a vertical nystagmus is evident in the left eye. To our knowledge this is the first reported case of an infant with noncomitant strabismus due to congenital toxoplasma cranial nerve involvement. The finding of an acquired third cranial nerve palsy accompanied by progressive neurologic sequelae warrants consideration of congenital toxoplasmosis.

Choroidal microvascular repair after argon laser photocoagulation.

We studied the repair process of the choriocapillaris after argon laser retinal photocoagulation in the domestic cat with a plastic injection-corrosion technique and scanning electron microscopy. Retinal scatter photocoagulation was applied to the tapetum at threshold-, moderate-, and high-intensity levels and specimens prepared one, ten, and 30 days later. At 24 hours after photocoagulation, obstruction of the choriocapillaris was always present regardless of the power used. In lesions produced by higher-intensity energy levels, choriocapillaris defects had larger diameters and larger vessels were affected more severely. At ten days, there were early signs of choriocapillaris repair. At 30 days, choriocapillaris occupied almost the entire area of the defect, although the normal lobular architecture was not present.

Topical delta 9-tetrahydrocannabinol and aqueous dynamics in glaucoma.

Systemic delta 9-tetrahydrocannabinol (THC), administered either by smoking marihuana or as synthetic THC in soft gelatin capsules, lowers ocular tension in various glaucomas, but at the expense of significant decreases in systolic blood pressure. Topical THC in light mineral oil vehicles, though effective in laboratory animals, was not shown effective in 0.05 and 0.1% topical solutions when administered to six subjects with primary open-angle glaucoma in a randomized, balanced, double-masked protocol. Light mineral oil, which has an affinity for corneal epithelium, is an optimum vehicle for administering drugs whose mechanisms of action are systemic rather than local within the eye. Further glaucoma research should therefore proceed with marihuanas containing insignificant levels of THC (less than 0.4%) and with various local delivery systems of the ocular-active cannabinoid found in Cannabis sativa.